/* Copyright (c) 2003 The Nutch Organization.  All rights reserved.   */
/* Use subject to the conditions in http://www.nutch.org/LICENSE.txt. */

/** JavaCC code for the Nutch lexical analyzer. */

options {
  STATIC = false;
  USER_CHAR_STREAM = true;
  OPTIMIZE_TOKEN_MANAGER = true;
  UNICODE_INPUT = true;
//DEBUG_TOKEN_MANAGER = true;
}

PARSER_BEGIN(NutchAnalysis)

package net.nutch.analysis;

import net.nutch.searcher.Query;
import net.nutch.searcher.QueryFilters;
import net.nutch.searcher.Query.Clause;

import org.apache.lucene.analysis.StopFilter;

import java.io.*;
import java.util.*;

/** The JavaCC-generated Nutch lexical analyzer and query parser. */
public class NutchAnalysis {

  private static final String[] STOP_WORDS = {
    "a", "and", "are", "as", "at", "be", "but", "by",
    "for", "if", "in", "into", "is", "it",
    "no", "not", "of", "on", "or", "s", "such",
    "t", "that", "the", "their", "then", "there", "these",
    "they", "this", "to", "was", "will", "with"
  };

  private static final Set STOP_SET = StopFilter.makeStopSet(STOP_WORDS);

  private String queryString;

  /** True iff word is a stop word.  Stop words are only removed from queries.
   * Every word is indexed.  */
  public static boolean isStopWord(String word) {
    return STOP_SET.contains(word);
  }

  /** Construct a query parser for the text in a reader. */
  public static Query parseQuery(String queryString) throws IOException {
    NutchAnalysis parser =
      new NutchAnalysis(new FastCharStream(new StringReader(queryString)));
    parser.queryString = queryString;
    return parser.parse();
  }

  /** For debugging. */
  public static void main(String[] args) throws Exception {
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    while (true) {
      System.out.print("Query: ");
      String line = in.readLine();
      System.out.println(parseQuery(line));
    }
  }

}

PARSER_END(NutchAnalysis)

TOKEN_MGR_DECLS : {

  /** Constructs a token manager for the provided Reader. */
  public NutchAnalysisTokenManager(Reader reader) {
    this(new FastCharStream(reader));
  }

}

TOKEN : {					  // token regular expressions

  // basic word -- lowercase it
<WORD: ((<LETTER>|<DIGIT>|<WORD_PUNCT>)+ | <IRREGULAR_WORD>)>
  { matchedToken.image = matchedToken.image.toLowerCase(); }

  // special handling for acronyms: U.S.A., I.B.M., etc: dots are removed
| <ACRONYM: <LETTER> "." (<LETTER> ".")+ > 
    {                                             // remove dots
      for (int i = 0; i < image.length(); i++) {
	if (image.charAt(i) == '.')
	  image.deleteCharAt(i--);
      }
      matchedToken.image = image.toString().toLowerCase();
    }

  // chinese, japanese and korean characters
| <SIGRAM: <CJK> >

   // irregular words
| <#IRREGULAR_WORD: (<C_PLUS_PLUS>|<C_SHARP>)>
| <#C_PLUS_PLUS: ("C"|"c") "++" >
| <#C_SHARP: ("C"|"c") "#" >

  // query syntax characters
| <PLUS: "+" >
| <MINUS: "-" >
| <QUOTE: "\"" >
| <COLON: ":" >
| <SLASH: "/" >
| <DOT: "." >
| <ATSIGN: "@" >
| <APOSTROPHE: "'" >

| <WHITE: ~[] >                                   // treat unrecognized chars
                                                  // as whitespace
// primitive, non-token patterns

| <#WORD_PUNCT: ("_"|"&")>                        // allowed anywhere in words

| < #LETTER:					  // alphabets
    [
        "\u0041"-"\u005a",
        "\u0061"-"\u007a",
        "\u00c0"-"\u00d6",
        "\u00d8"-"\u00f6",
        "\u00f8"-"\u00ff",
        "\u0100"-"\u1fff"
    ]
    >

|  <#CJK:                                        // non-alphabets
      [
       "\u3040"-"\u318f",
       "\u3300"-"\u337f",
       "\u3400"-"\u3d2d",
       "\u4e00"-"\u9fff",
       "\uf900"-"\ufaff"
      ]
    >    

| < #DIGIT:					  // unicode digits
      [
       "\u0030"-"\u0039",
       "\u0660"-"\u0669",
       "\u06f0"-"\u06f9",
       "\u0966"-"\u096f",
       "\u09e6"-"\u09ef",
       "\u0a66"-"\u0a6f",
       "\u0ae6"-"\u0aef",
       "\u0b66"-"\u0b6f",
       "\u0be7"-"\u0bef",
       "\u0c66"-"\u0c6f",
       "\u0ce6"-"\u0cef",
       "\u0d66"-"\u0d6f",
       "\u0e50"-"\u0e59",
       "\u0ed0"-"\u0ed9",
       "\u1040"-"\u1049"
      ]
  >

}


/** Parse a query. */
Query parse() :
{
  Query query = new Query();
  ArrayList terms;
  Token token;
  String field;
  boolean stop;
  boolean prohibited;

}
{
  nonOpOrTerm()                                   // skip noise
  (
    { stop=true; prohibited=false; field = Clause.DEFAULT_FIELD; }

                                                  // optional + or - operator
    ( <PLUS> {stop=false;} | (<MINUS> { stop=false;prohibited=true; } ))?

                                                  // optional field spec.
    ( LOOKAHEAD(<WORD><COLON>(phrase(field)|compound(field)))
      token=<WORD> <COLON> { field = token.image; } )?

    ( terms=phrase(field) {stop=false;} |         // quoted terms or
      terms=compound(field))                      // single or compound term

    nonOpOrTerm()                                 // skip noise

    {
      String[] array = (String[])terms.toArray(new String[terms.size()]);

      if (stop && terms.size()==1 && isStopWord(array[0])) {
        // ignore stop words only when single, unadorned terms
      } else {
        if (prohibited)
          query.addProhibitedPhrase(array, field);
        else
          query.addRequiredPhrase(array, field);
      }
    }
  )*
  
  { return query; }

}

/** Parse an explcitly quoted phrase query.  Note that this may return a single
 * term, a trivial phrase.*/
ArrayList phrase(String field) :
{
  int start;
  int end;
  ArrayList result = new ArrayList();
  String term;
}
{
  <QUOTE>

  { start = token.endColumn; }
  
  (nonTerm())*                                    // skip noise
  ( term = term() { result.add(term); }           // parse a term
    (nonTerm())*)*                                // skip noise

  { end = token.endColumn; }

  <QUOTE>
    
  {
    if (QueryFilters.isRawField(field)) {
      result.clear();
      result.add(queryString.substring(start, end));
    }
    return result;
  }

}

/** Parse a compound term that is interpreted as an implicit phrase query.
 * Compounds are a sequence of terms separated by infix characters.  Note that
 * htis may return a single term, a trivial compound. */
ArrayList compound(String field) :
{
  int start;
  ArrayList result = new ArrayList();
  String term;
}
{
  { start = token.endColumn; }

  term = term() { result.add(term); }
  ( LOOKAHEAD( (infix())+ term() )
    (infix())+
    term = term() { result.add(term); })*

  {
    if (QueryFilters.isRawField(field)) {
      result.clear();
      result.add(queryString.substring(start, token.endColumn));
    }
    return result;
  }

}

/** Parse a single term. */
String term() :
{
  Token token;
}
{
  ( token=<WORD> | token=<ACRONYM> | token=<SIGRAM>)

  { return token.image; }
}


/** Parse anything but a term or a quote. */
void nonTerm() :
{}
{
  <WHITE> | infix() | <EOF>
}


/** Parse anything but a term or an operator (plur or minus or quote). */
void nonOpOrTerm() :
{}
{
  (LOOKAHEAD(2) (<WHITE> | nonOpInfix() | ((<PLUS>|<MINUS>) nonTerm())))*
}

/** Characters which can be used to form compound terms. */
void infix() :
{}
{
  <PLUS> | <MINUS> | nonOpInfix()
}

/** Parse infix characters except plus and minus. */
void nonOpInfix() :
{}
{
  <COLON>|<SLASH>|<DOT>|<ATSIGN>|<APOSTROPHE>
}